pick

Type: object

Signature: object.pick(keys)

What It Is

object.pick(keys) is used here as a contract-first parser powered by document-level structure checks, explicit section targeting, and typed field extraction for pick scenarios. With object(), string(), min(), and document() in the schema, 1 h1 heading and 1 h2 section is converted into top-level keys title and data without manual pick post-processing. Error cases report issue codes like string_too_short, making operational diagnostics for pick flows consistent across local runs and CI.

When to Use

This method is a strong fit for composing reusable object contracts across related markdown schemas where deterministic pick parsing matters more than free-form flexibility. Do not default to it for one-off payloads where object composition adds no reuse value around pick; the main cost is key-level strictness that improves typing but rejects ad-hoc variations. For best results, compose object.pick(keys) with object(), string(), min(), and document() so pick schema intent stays readable and output remains predictable.

object.pick(keys)

Input Markdown

# RUNBOOK: Object Pick

## 0. META

- service: fraud-api
- owner: risk-platform

Schema

import { md } from '@markschema/mdshape'

const base = md.object({
  service: md.string().min(3),
  owner: md.string().min(3),
})

const schema = md.document({
  title: md.heading(1),
  data: md
    .section('0. META')
    .fields({
      service: md.string().min(3),
      owner: md.string().min(3),
    })
    .pipeline(base.pick(['service'])),
})

Result

Success

{
  "success": true,
  "data": {
    "title": "RUNBOOK: Object Pick",
    "data": {
      "service": "fraud-api"
    }
  }
}

Error

Failure trigger: The input violates one or more constraints declared in the schema; use issues[].path and issues[].code to locate the exact failing node.

{
  "success": false,
  "error": {
    "issues": [
      {
        "code": "missing_heading",
        "message": "Missing heading with depth 1",
        "path": [
          "title"
        ],
        "line": 1,
        "position": {
          "start": {
            "line": 1,
            "column": 1
          }
        }
      }
    ]
  }
}